A series of methionine analogs, S-adenosylmethionine analogs and S-adenosylsulfonium salts are being prepared and investigated as antitumor agents in intact animals and tissue cultures. These compounds will also be evaluated in vitro as inhibitors of ATP:L-methionine adenosyltransferase and the tRNA methylases. Antitumor activity will be correlated with ATP:L-methionine adenosyltransferase and tRNA methylase inhibition.